Cold sensitivity of the SARS-CoV-2 spike ectodomain.
The impact of COVID-19 and the urgency to develop a vaccine against the SARS-CoV-2 virus cannot be overstated. The viral fusion spike (S) protein ectodomain is the primary target for vaccine development. Here we report an unexpected cold sensitivity of a stabilized SARS-CoV-2 ectodomain construct currently being widely used for immunogen design. We found that when stored at 22 or 37 °C for 1 week, the S-protein displayed well-ordered trimeric spikes by negative stain electron microscopy. However, storage at 4 °C reduced the trimeric spikes to <10%, accompanied by decreased stability and enhanced exposure of the ACE-2 receptor binding site. Well-formed S particles could be recovered from cold-stored samples by a brief incubation at 37 °C. Our results will have broad impact on structural, functional and vaccine studies using the SARS-CoV-2 S ectodomain. Highlights: SARS-CoV-2 S ectodomain construct, widely used for vaccine studies, exhibits cold sensitivity.Negative stain electron microscopy shows disintegration of spike structure upon storage at 4 °C.Differential scanning calorimetry measurements confirm destabilization by cold.Cold storage alters antigenicity of SARS-CoV-2 spike.Brief incubation at 37 °C restored spike integrity after cold-storage.
Edwards, RJ; Mansouri, K; Stalls, V; Manne, K; Watts, B; Parks, R; Janowska, K; Gobeil, SMC; Kopp, M; Li, D; Lu, X; Mu, Z; Deyton, M; Oguin, TH; Sprenz, J; Williams, W; Saunders, K; Montefiori, D; Sempowski, GD; Henderson, R; Alam, M; Haynes, BF; Acharya, P
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